! [new branch] debian/master -> origin/debian/master (unable to update local ref)

[knorrie]

PSA: I'm converting the debian branches of this repo to DEP14 format.

That means that we'll have debian/master and debian/stretch-backports etc.

For whoever has cloned this repo before, this will result in the error shown in the subject, when trying to fetch updates:

error: cannot lock ref 'refs/remotes/origin/debian/master': 'refs/remotes/origin/debian' exists; cannot create 'refs/remotes/origin/debian/master'
 ! [new branch]      debian/master            -> origin/debian/master  (unable to update local ref)
error: cannot lock ref 'refs/remotes/origin/debian/stretch-backports': 'refs/remotes/origin/debian' exists; cannot create 'refs/remotes/origin/debian/stretch-backports'
 ! [new branch]      debian/stretch-backports -> origin/debian/stretch-backports  (unable to update local ref)

The git client might suggest:

error: some local refs could not be updated; try running
 'git remote prune origin' to remove any old, conflicting branches

As long as you don't have a local branch based on the old upstream debian, just follow the instruction once, and you'll be fine.